COMPOSTING 101 Why compost?..................................................................................................................... 2 Materials............................................................................................................................. 3 Passive Composting ........................................................................................................... 4 Backyard composting......................................................................................................... 4 Moisture & Heat ................................................................................................................ 4 Bin/Pile Information.......................................................................................................... 5 How to Compost................................................................................................................. 5 Nitrogen.......................................................................................................................... 5 Carbon............................................................................................................................. 5 Water............................................................................................................................... 5 Air.................................................................................................................................... 6 Size.................................................................................................................................. 6 Composting Techniques .................................................................................................... 6 How to Tell When it's Done............................................................................................... 7 Backyard Composting Dos: ............................................................................................... 8 Backyard Composting Don'ts: ........................................................................................... 8 Troubleshooting ................................................................................................................. 9 Why compost? Composting recycles or "downcycles" organic household and yard waste into an extremely useful end-product called compost. Examples are fruit or vegetable kitchen waste and yard clippings. Ultimately this permits the return of needed organic matter and nutrients into the foodchain and reduces the amount of "green" waste going into landfills. It is important to distinguish between terms such as "biodegradable", "compostable", and "compost-compatible". • A biodegradable material is capable of being broken down completely under the action of microorganisms into carbon dioxide, water and biomass. It may take a very long time for a material to biodegrade depending on its environment (e.g. hardwood in an arid area), but it ultimately breaks down completely. • A compostable material biodegrades substantially under composting conditions, into carbon dioxide, methane, water and compost biomass. Compost biomass refers to the portion of the material that is metabolized by the microorganisms and which is incorporated into the cellular structure of the organisms or converted into humic acids etc. Compost biomass residues from a compostable material are fully biodegradable. "Compostable" is thus a subset of "biodegradable". The size of the material is a factor in determining compostability because it affects the rate of degradation. Large pieces of hardwood may not be compostable under a specific set of composting conditions, whereas sawdust of the same type of wood may be. • A compost-compatible material does not have to be compostable or even biodegradable. It may biodegrade too slowly to be compostable itself, or it may not biodegrade at all. However, it is not readily distinguishable from the compost on a macroscopic scale and does not have a deleterious effect on the compost (e.g. it is not a biocide). Compost-compatible materials are generally inert and are present in compost at relatively low levels. Examples of compost-compatible materials include sand particles and inert particles of plastic. Although composting has historically focussed on creating garden-ready soil, it is becoming more important as a tool for reducing the solid waste stream. More than 60 percent of household waste in the United States is recyclable or compostable. But Americans only compost 8 percent of their waste. Surveys have shown that the #1 reason Americans don't compost their waste is because they feel the process is complicated, time-consuming or requires special equipment. However, especially in rural areas, much of the solid waste could be removed from the waste stream by promoting "extremely passive composting" where consumers simply discard their yard waste and kitchen scraps on their own land, regardless of whether the material is ever re-used as "compost". Materials Many different materials are suitable for composting organisms. Composters often refer to the carbon to nitrogen ratio requirements; some materials contain high amounts of carbon in the form of cellulose which the bacteria need for their energy. Other materials contain nitrogen in the form of protein, which provide nutrients for the energy exchanges. It would however be an over-simplification to describe composting as about carbon and nitrogen, as is often portrayed in popular literature. Elemental carbon - such as charcoal - is not compostable nor is a pure form of nitrogen, even in combination with carbon. Not only this, but a great variety of man- made, carbon-containing products, including many textiles and plastics are not compostable. For home-scale composting, mixing the materials as they are added increases the rate of decomposition, but it can be easier to place the materials in alternating layers, approximately 6 inches thick, to help estimate the quantities. Keeping carbon and nitrogen sources separated in the pile can slow down the process, but decomposition will still occur. Some people put special materials and activators into their compost. A light dusting of agricultural lime can curb excessive acidity, especially with food waste. Seaweed meal provides a ready source of trace elements. Finely pulverized rock (rock flour or rock dust) can also provide minerals, while clay and leached rock dust are poor in trace minerals. Some materials are best left to a “commercial” composting system, as they decompose slower, attract pests and require higher temperatures to kill disease causing organisms than backyard composting provides. These materials include meat, dairy products, eggs, restaurant grease and cooking oil. Aerated composting is an efficient form of composting from the chemical point of view as it produces ultimately only energy in the form of waste heat and CO2 and H2O . With aerated composting, fresh air (i.e. oxygen) is introduced throughout the mix of materials using any appropriate mechanism. The air stimulates the microorganisms that are already in the mix, and their by-product is heat. In a properly operated compost system, pile temperatures are sufficient to stabilize the raw material, and the oxygen-rich conditions within the core of the pile eliminate offensive odors. High temperatures also destroy fly larvae and weed seeds, yielding a safe, high-quality finished product. Finally, aeration expedites the composting process through the mechanism of heating; elevated heat will drive biochemical processes faster, so that a finished product can be rendered in 60 to 120 days. Aerated compost is an excellent source of macro- and micro-nutrients as well as stable organic matter, all of which support healthy plant growth. In addition, the micro-organisms in compost aid in the suppression of plant diseases. Finally, compost retains water extremely well resulting in improved drought resistance, a longer growing season, and reduced soil erosion. Passive Composting Passive composting is composting in which the work needed to mix and turn the compost pile is kept to a minimum, and often as a result, the temperatures never reach much above 86 °F. It is slower but is the more common type of composting in most domestic garden compost bins. Kitchen scraps are put in the garden compost bin and left untended. This scrap bin can have a very high water content which reduces aeration, and so becomes odorous. To improve drainage and airflow, a gardener can mix in wood chips, small pieces of bark, leaves or twigs, or make physical holes through the pile. Backyard composting Home composters use a range of techniques, varying from extremely passive (throw everything in a pile and leave it for a year or two) to extremely active (monitor the temperature, turn the pile regularly, and adjust the ingredients over time). Some composters use mineral powders to absorb smells, although a well-maintained pile seldom has bad odors. Moisture & Heat An effective compost pile is about as damp as a well wrung-out sponge. This provides the moisture that all life requires. Microorganisms vary by their ideal temperature and the heat they generate as they digest. Mesophilic bacteria survive best at temperatures of 20 to 44 °C (70 to 120 °F). Thermophilic (heat-surviving) bacteria grow optimally at around 55°C (130 °F), and can attain the fastest decomposition, since metabolic processes proceed more rapidly under higher temperatures. Elevated temperature is also preferred since it causes the most